Biomass gasification-based generators are an attractive method for power generation, as these gasifiers are fueled with carbonaceous byproducts that are inexpensive and often free to source. However, these potentially useful byproducts come in all shapes and sizes, and gasifiers are typically highly sensitive to fuel particulars. Gasifiers usually will not operate properly on fuel larger or smaller than a predetermined range. Therefore, gasifier operation typically involves a great deal of fuel pre-processing, whether by chopping material down to a desired size through chippers or shredders, or building the material up to the threshold size via a densification process.
Typical fixed bed downdraft gasifiers are relatively simple and are capable of making engine grade syngas, but can only do so with large chunk fuel. If fed a fine grain fuel, fixed bed gasifiers tend to have problems with tar, as well as problems with mechanical packing in the reduction zone (gasification zone). Kinetic bed gasifiers, such as fluidized beds or cyclonic reactors, can mechanically process fine fuels. However, kinetic bed gasifiers mix all the gasification zones together, and produce a tarry gas that requires downstream cleanup. Kinetic bed reactors also tend to be very large and complicated, requiring elaborate controls and multiple vessels.
What is needed is a gasifier that can, over a wide range of fuel sizes, maintain good zone separation for low tar gas, simultaneous with good mechanical handling and throughflow, and do so at relatively low cost and complexity. In particular, a gasifier that can produce low tar syngas from fine fuels would be particularly valuable, as biomass byproducts are most commonly found in smaller sizes, and reducing biomass size is much easier than increasing biomass size through densification. Thus, there is a need in the field for a new gasifier design that will produce engine grade gas from small fuels without the complication of previous systems. There is an even greater need for a new gasifier design that will produce engine grade gas from any shape or size fuel, approximating a fuel agnostic gasifier, and do so with low system complexity, minimized size, and ease of operation for the user. This invention provides such new and useful gasifier.